Mechanical device for converting rotary motion into reciprocatory motion, and vice versa



Nov. 25, 1947. MclLRATH 2,431,493 7 MECHANICAL DEVICE FOR CONVERTINGROTARY MOTION INTO RECIPROCATORY MOTION AND VICE VERSA I Filed July 211944 2 Sheets-Sheet 1 Nov. 25, 1947. H. MCILRATH 2,431,493

MECHANICAL DEV FOR CONVERTING ROTARY MOTION INTO RECIPROCA'TORY MOTIONAND VICE VERSA Filed July 21. 1944 2'Sheets-Sheet '2 Patented Nov. 25,1947 MECHANICAL DEVICE FOR CONVERTING ROTARY MOTION INTO RECIPROCATORMOTION, AND VICE VERSA James Hugh McIlrath, Hatfield, Pretoria,Transvaal, Union of South Africa Application July 21, 1944, Serial No.545,912. In the Union of South Africa September 29, 1943 4 Claims.

This invention relates to an improved mechanical device for the purposeof converting rotary motion into reciprocatory motion and vice versa.

According to the invention the device comprises two spaced parallelcranks or the equivalent, which are positively interconnected so thatthey can be caused to rotate in the same direction and at the sameangular velocity, and a slotted lever arm connecting said cranks or thelike which are so set relatively to one another that on rotation thereofan end of said slotted lever arm by being guided can be made to transmitrectilinear reciprocatory motion to a working part connected thereto andvice versa.

It is to be understood that the relative setting of the two cranks orthe like is such that, during rotation, they alternativel approach andrecede from one another with the result that the moments of leveragevary from a maximum to a minimum during each complete revolution.Actually the device is in the nature of a lever fulcrumed intermediatelyof its ends and having a continuously moving fulcrum as well as acontinuously moving point of application of the levering force.

From the aforegoing description it will be understood that the mechanismgives a quick return motion which makes it suitable for numerousapplications. The device is particularly suitable for use as a powerhead for a pump.

The two cranks or the like form part of or are driven by two parallelshafts which are interconnected by spur or chain gearing. In one formthe cranks are formed by crank pins projecting from the faces of twogear wheels each mounted on the end of a shaft which two shafts areinterconnected by the provision of an idler gear wheel or pinionarranged between and meshing with both the aforesaid gear wheelscarrying the crank pins. Alternatively a chain drive may be employed tosynchronize the rotary motion of the two shafts.

The said lever arm need only be slotted where it engages with the crankpins.

When the device forms the power head of a pump, the operative end of thelever arm is connected to a cross-head arranged for vertically slidingmovement on suitable guides, while the pump rod is connected to thecross-head.

An advantage of the device is that a relatively long stroke can beobtained by the use of relatively small diameter crank wheels or thelike since the extent of movement of the operative end. of the lever armis largely governed by the device constructed according to theinvention,

and adapted for use as a power head for a pump.

Figure 2 is a plan view, taken of the device shown in Figure 1.

Figure 3 is an end view of the device shown in Figures 1 and 2, and

Figure 4 is a view similar to Figure 1, but showing one crank having agreater throw than the other.

Referring to the drawings, references I and 2 denote the two cranks, theshafts of which on one side are journalled in bearings 3 and 4, while onthe other side the shafts are journalled in bearings 5 and 6, where theyhave keyed to them the gear wheels 7 and 8 which both mesh with the gearpinion 9 which is adapted to be driven by the pulley ID.

The two cranks l and 2, are connected to the slotted lever arm I l bymeans of the sliding crossheads l2 and I3. The front end of said slottedlever II is guided by means of the slipper l4 engaging with the verticalguide rod I5.

The pump rod I6 is likewise attached to the front end of said slottedlever arm II, as clearly shown in Figure 1.

The full-line position of the slotted lever arm II in Figure 1represents the bottom position or end of the downward stroke. The arrowsin Figure 1 indicate the direction of rotation of the gear wheels andpinion. As shown in Figure 1, the lever arm II is just about to commenceits upward stroke, and it will be noted that, as the cranks I and 2rotate in the directions indicated, they will be at the furthestdistance apart when the slotted lever arm H has reached the midstrokeposition, that is on the upward stroke. The broken line outline showsthe position at the top of the stroke. On the downward stroke the cranksl and 2 approach one another, and at mid-stroke they will be in linehorizontally, and therefore at their nearest positions to one another.It will accordingly be understood from 3 the above description, that agreater mechanical advantage is obtained on the upstroke than on thedown stroke, which naturally gives a quickretum motion.

As illustrated, the two cranls l and 2 have the same throw. Theinvention is, however, not limited in this respect since one crank orits equivalent may be arranged to have a larger throw than the other,depending upon the duty required from the mechanism.

Figure 4 shows this modification in which the crank arm 20 of the gearwheel I is substantially longer than the crank arm of the gear wheel 8.

What I claim is:

1. A device for converting rotary motion to v reciprocatory motion andvice versa which comprises, two spaced cranks, means interconnectingmeans associated with one end of said lever am, said end of said leverarm moving in a rectilinear reciprocatory path.

2. A device as claimed in claim 1 wherein the means interconnecting saidcranks is gearing.

3. A device as claimed in claim 1 wherein said cranks are of equalthrow.

4. A device as claimed in claim 1 wherein said cranks are of unequalthrow.

JAMES HUGH MGILRA'I'H.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 317,929 Cox May 12, 18851,804,577 Walter May 12, 1931 FOREIGN PATENTS Number Country Date618,473 France Mar. 10, 1927

